Catalytic esterification of glucosides with fatty acids



Unit-Cd tes Patent "GATABYTIC ESTERIFICATIGN' OFGLUCQSIDES WITH FATTY ACIDS John P, Gibbons, Pittsburgh, Pa. assignor to Corn Prodeucts Refining Company, New YorkpN; Y.,. a corpora" -=tion-oE NewtIersey N Dr win A p cat n Jun 1 .,Serial No, 294,936

::19 Glaims. 1 (Cl; 260-210) in nt o vm at d ith z product n o we t i a o .slycosidesm and "m r part ula ly to he p oducti .o rtat vea idr s er -of: g vcqsi es; bytd re. .t sterifi tio -ao zerslc side .with: arfattv acid. rflhew lassical hodiforz he p rarationzofiat vac 1. 1. 1 f. glv o id malov r-the .I'QQCt'i T l r'glvco i with. h iifat y-tacidh liderilsna yz in rtherr en eofian excess of an organic base, such as quinoline or pyridine, which Combines with the" hydrogen halide formed by the react o .Upo o np etion.o ...th .esteriti ation, r a tion mixture. is PQuredjnto. col wa er, rom, wh c 1h s,ter is xtra.t w t awat immiscib s lven Ihle mde...es .r. .is. then v-x. b.t .1. ne (t a th ext t by distillingnfl thesolvent.

Tbi m tho .i co y: forcomm ci p od c io o iat y acid est r .of s v os desa ecause .ofu heplet gthv n o ss n --a "-n me ons.t teu equir d, in addition .1

the .ta tnliat.th i t va h l de v a t nsidera rm re flgPsmsivethan ,the, ,free -fatty .aCid.

How ve i ec terificatio i o 1yos de :o th tre .f ttvwac dslha b n -fo ndt e .u fasib v. .t e.1 .s1 a

.cohols. These ,procedures." utilize strongly, acidiq cataly ine; gasfl l r or hy r c ori ac t :btineabou .th ereaetionof t e alco o h thm attv-aci W-heni is attempted to esterify directly glycosides by such methods, extensive degradatiomof the glycosides occurs, as evidenced: bye. excessive rn ramelizati n; e en ua y, complete:carbonizatiom of ithe ;re action1m t1; KS ingtineextremelyrpoor yields; atbest.

a "20.111: copendingapPlicatiomz-Serial 151p. 1294,93 7, filed -June'21, 1952, describesz aemethodwherebyglycosides canfibei-directlyeesterifiedewith i-free fatty apids, without appreciableedestructionref the;;gly, side an withggogd yields of 'thee esters, by heating armirrtureg ofiithesglycos'i'cleeandifreevfatty.acidmnderlcontrolled condition Without zi -catalyst.

It has been furthertdiscovered,:however,;that. glycosides can also' be I directly esterified lvvitlm free; s fatty acids iby heating the glycoside-:andltherfireesfattymcidmnder controlled conditions in thQgRIQSQILCC of an alkaline cata- 2,759,923 :e-P atentedaA-ugn 2 1 2512956 ice invention :is to providea process for direct esterification .of glycosides with reduction in color formation 1 andiwith shorter reactiomperiods. It-is alsoan object of this in- -vention toprovide a-catalytic method foresterification 5 of glycosides. Otherobjects'andadvantages will appear lyst. The use of the alkaline'catalyst presents the ad- 7 than was possible heretofore. A further object of this hereinafter.

Thepresent invention comprises heat-ing the free fatty acid-with a glycoside'in the presence of --an alkaline cata- :lyst --at- -temperat1ires-within the range of about 16 -'C. to about 300 'C.-until=the* desired;- degreeof esterification "has been attained.

Diesters, trie'sters, and tetraesters-maybe prepared by the process-of this invention by appropriate control or the reaction time, temperatureand/ or ratioof reactants.

Glyc osides of the hexoses, pentoses, and other sugars may be employed "in thepresent process. Advantageous- 1y *theyshould be of high, purity, containing substantiall no freemineral'acid andonly minimum arnountsof Qfree sugar, if'any; in order to avoid undesirable side'reactions giving rise to'extremely dark colored products.

"The-fatty acids suitable for'use' infthis invention'are 'thosewhich contain'from' 6 'to"20car bon atoms in their jaliphatic fch ai n's. "Both saturated and unsaturated fatty acids, in the pure state or as mixtures, such as are oblai ed. .bvt h sa onifi a i p ve e b oils, dsvn- ,thetic niiggtures ofifatty acids are suitable. Some example o s i b e ta v. acid a pf 'oi J aur r p lm ic, 'olei .tearic,llin le c, an -.li o e i c d as Well as' h fatty. c d .o -dehydra e wca t ;9, ns e o .9 o .aaldsovhean o Qbv ously i mi r of t y acids "are employed, mixed esters will bejobtained.

Th al aline catalyst su tab e. o ii e.v n. he pre .nmce nlus1 ..me a -ox de an .;hvd 2 ide g- ;t ka met-filJl Yd Dfide an alkal n ea h-ox e a .vve ,,a k l ;.an .alka ee r sal o ...a 1 e. g. acetic acid. Examples of suitable catalysts include .lithatg ba ium: a et calciu ace a ,v sodium 3- r x derand z al -.X d M xt re f u mfa e al may also be employed.

I .Ie ot f cosidaio-fiee at y. ac d. e ploye in he rea t on. 5 noteuca ,texceptlth tth a o to free fatty acid must be, obviously,,. at;leastequivalentto that theoretically required to produce the desired degree of esterifications; i. exit-a tetraester is desired, at least 4 :molsof :ta tyta idr-zw b n ce s .S m v; if a --d -ir;tti st r:i r esired, tile t =0 ,.-.m s,rr. pe t 3 v, of a y. -m stbe empl ye o su sta ia y'eq .pletelyeconvert ,ithe=gglycoside to :the corresponding-ester. However, aneexcessoff attyacid-maybe used-if desired.

.LWhen. .an. excess" of fatty, 1 acid over; that theoretically requiredztoqproduce :the desired -:6S tl" is :employed in-the .ca-se L-of zdi-L .andctriesters,: the .degree of esterification :is controlled byJsuitable choicerof reaction -conditions,-,such was. temperatures and: Lreaction1: tin1e,-J.Which .are sinterdependent variables.

fihetamount of.catalyst employed is not: critical. "Howeversiamounts within -the range 'of. about I0;05 J percent to about OiS-percent will ..usually .be -satisfactory, although ;lar-ger---or smaller percentages of catalyst .may the temployedyifdesired.

The ternperatilre utilized -to accomplish the esterifica- -tion-is important, :since too high a temperature tends to produce undesirable side :reactions,Whereas-too-low a temperature results inextremely slow rates of est-erification. Temperatures within the range of about C. to-abput "300fC. givegoqd yields of esters of desirable quality within ai reasonable length of time, and, "thereforejare preferred.

lnfrnany casesthe color ofthe final product'may; be improved by maintaining the temperature at the beginning "of" the reaction at the lower end of the range and increasing the temperature, preferably stepwise, as the esterification proceeds.

For example, the temperature may be maintained below 200 C. until the esterification is about 50 percent completed, then above 200 C. for the remainder, or the temperature may be maintained within the lower portion of the aforesaid range until the esterification is approximately 75 percent completed, and thereafter increased preferably to about 230 C. to about 250 C., until the esterification is completed. The latter procedure is especially suitable when preparing a tetraester. The progress of the esterification may conveniently be followed by measuring the amount of water liberated in the reaction, which will be discussed more fully hereinafter.

The reaction time depends upon the temperature employed, the particular reactants involved, the degree of esterification desired (di-, tri, or tetraester), and also to some extent upon Whether or not the water of esterification is removed as formed.

Since esterification is a reversible reaction in the presence of water, and water is one of the pro-ducts formed in a direct esterification, it is advantageous to provide means for removal of the water of esterification as it is formed in order to force the esterification to substantial completion. It is also advantageous to agitate the reaction mixture during the esterification, as this tends to increase the esterification rate somewhat and also to give a more uniform heat distribution throughout the reaction mixture.

The removal of the water is facilitated, and hence the reaction rate increased, by the application of a slight vacuum to the system. The removal of water is convenie'ntly accomplished by the addition to the reaction mixture of a substance which forms an azeotrope with water, e. g. benzene, toluene, or xylene. Such addition also accelerates the reaction rate.

Passage of an inert gas such as nitrogen or carbon dioxide, over the surface of the reaction mixture although not essential, particularly when an azeotrope is employed for removal of water, tends to improve the color of the final products.

The glucoside esters produced according to the process of this invention are particularly useful as drying oils, for example, in varnishes.

The following examples, which are intended as typical and informative only and not in a limiting sense, will further illustrate the invention:

Example 1 284.1 grams (equivalent to 1 mol) of linseed oil fatty acids (Acid No. 197.5), 48.5 grams methyl alpha-D- gluco-side (equivalent to 0.25 mol) and 0.14 gram of litharge (0.05% on the weight of fatty acids) were placed in a three liter 3-necked flask equipped with a water distilling trap (Dean-Stark tube) attached to a reflux condenser, thermometer, gas inlet tube and a mechanical stirrer. While agitating in an atmosphere of carbon dioxide, the mixture was heated as rapidly as possible to 165 C. by means of a hemispherical electric mantle. At this point xylene was added through the condenser to entrain 2 the water of esterification. The reaction was held between 200 C. and 220 C. for 2 hours, at 235 C. for 2 hours, and finally at 250 C. to 270 C. for 2 hours. After jetting off the xylene with carbon dioxide and cooling to room temperature, the yield was 311.5 grams of a red oil with an acid number of 22 (88.8% ester), a saponification number of 177.5, a Hellige color of 154 and a Gardner viscosity of 500 centipoises.

Example 2 phere. At this point xylene was added to form an azeotrope with the water of reaction. The temperature was maintained between 225 C. and 235 C. for an additional 7 hours. After removing the xylene by jetting with nitrogen and cooling to room temperature, the yield was 1336 grams of a red oil with an acid number of 25.4 (87.3% ester), a saponification number of 181, a Hellige color of 16 and a Gardner viscosity at 25 C. of centipoises.

Example 3 In an apparatus similar to that described in Example 1, 141 grams of linseed oil fatty acids (Acid No. 199- equivalent of 0.5 mol), 24.3 grams of methyl alpha-D- glucoside (0.125 mol), and 0.14 grams of magnesium oxide was heated rapidly to C. while sparging with carbon dioxide. At this point xylene was added to remove water by azeotropic distillation. The following heating cycle was then employed: 2 hours at 195 C. to 197 C., 2 hours at 216 C. to 220 C., 2 hours at 230 C. to 231 C. and finally at 250 C. to 252 C. for an additional 2 hours. After jetting off the xylene with carbon dioxide and cooling to room temperature, the yield was 153 grams of a dark-colored oil. The product had an acid number of 18.1 (91.9% ester), a saponification value of 181, a Hellige color of 16, and a Gardner viscosity of 200 centi poises.

Example 4 In an apparatus similar to that described in Example 1, 290 grams (equivalent to 1 mol), of oleic acid (Acid N0. 195), 97 grams of methyl alpha-D-glucoside (0.5 mol) and 1.25 grams of sodium hydroxide was heated as rapidly as possible to 173 C. while stirring in an atmosphere of nitrogen. At this point toluene was added for azeotropic removal of the water of esterification. The temperature was maintained between 173 C. and 194 C. for 6 hours. The reaction mass was then allowed to cool to room temperature and dissolved in a liter of equal volume of benzene and methanol. This solution was treated under reflux for 1 hour with 50 grams of activated (Nuchar W), filtered and the solvent removed from the filtrate by distillation. The yield was 361 grams of a red oil having an acid number of 12.3 (93.7% ester), a saponification number of 150.5 and a Hellige color of 15.

Example 5 In an apparatus similar to that described in Example 1, 282 grams (equivalent to 1 mol) of stearic acid (Acid No. 199), 48.5 grams of methyl alpha-D-glucoside (0.25 mol) and 0.85 gram of calcium oxide was heated rapidly to 174 C. while agitating and sparging with carbon dioxide. Xylene was then added to entrain the water of esterification. The reaction was held between C. and 200 C. for 2.8 hours,.and then between 230 C. and 250 C. for an additional 9.5 hours. After jetting off the xylene with carbon dioxide and cooling to room temperature, 311 grams of a dark brown waxy solid was obtained which had an acid number of 17.8 (91.1% ester) and a saponification number of 178.5.

Example 6 In an apparatus similar to that described in Example 1, 402 grams (equivalent to 2 mols) of lauric acid (Acid No. 279), 97 grams of methyl alpha-D-glucoside (equivalent to 0.5 mol) and 0.4 gram of calcium oxide was heated rapidly with agitation and carbon dioxide sparging to 165 C. Xylene was then added to azeotropically remove water of esterification. The reaction temperature was held between 177 C. and 180 C. for 3 hours, between C. and 200 C. for 2.5 hours, at 215 C. for 1 hour, then at 230 C. for 1.7 hours, and finally between 245 C. and 248 C. for 4 hours. After jetting off the xylene and unreacted lauric acid at 248 C. with carbon dioxide, the product was cooled to roomtemperature, dissolved in 1000 ml. of benzene and decolorized by refluxing for 1 hour with 50 grams of activated carbon (Nuchar W). The carbon was filteredtofii. and..the.ben-.

zene: removed. from thehfiltrate. by. distillingdn. .vacuo.

The yield. was 381= grams. of a..light.tanroil-witlnan, acid. number. of 14.7. (94.7%. esterr); a saponificationnumbeu 01323.4- and a, Hellige color of 8.

Example 7' In an apparatus similanto that described in Example 1;

2115 grams (equivalent: to 0275 mol) of stearic acid" (Acid No. 199 48i5'gramstof methylalpha-D-glucoside (equivalentto 0.25 mol), 0.64 gram of calcium oxide and 13 grams of activated carbon (Nuchar W )'-was heated" rapidly to 165 C. while-stirring in an atmosphereof carbon dioxide. esterifi'cation by entrainment. Thetemperature was maintained between 185 C. and 205 C. for 6 hours. After jettingotf the xylene and cooling to room temperature the-product was dissolved in benzene and *thecarbon' filtered-01f; Tothe'filtrate was added 13 gramsof acti vatedficarbon' and the resulting solution refluxed for'l hour; ping ofii the-bcnzene, 216 grams of'a light tan; wax=likesolid was obtained, which had a melting point of501 54 C., an acidnumber of 21.7 (89.1% ester) ,and*a saponificationgnumber of 1715.

One hundred grams. of this ester was dissolved in' a literof ether under reflux, and the solution was'washed' With six 50 .ml. portions of 2 percent: aqueous sodium carbonate in. a separator-y funnel. oflthesodium carbonate by washing with. Water andj'the" ether by distillation, 75.1 grams of a light. brown wax.

was.rccoveredwhichhad amelting point of 52'-54 C.','

and'acid number of 1.2. (99.4% ester), andla saponifical: tionyalue .of"171.

Example 8 In an apparatus similar to that described in Example 1, 139.9 grams-(equivalent to'0l5mol)--of linseed oil fatty acids (Acid No."200'. 2715 grams-i(equivalent to 0.125 mol) of;.allyl alpha-D-glucoside 85%.9.0%, M..P...85.. 901 C., ,reducii1g sugar 0.35%) and. 0.14. gram oftcalcium oxide was heated rapidly to 194 CIwhile agitating;and sparging with carbon dioxide. Xylene was added to entrain the water of esterification-andthe-temperature maintained between 194 C. and; 204= C. for 6.75.:Hours. The xylene was then.removed.by bubbling through the reaction mixture a rapid'stream of carbon dioxide. On cooling to room temperature, the yield was 1'62-grams of a dark red oil with an acid number of 56.6 (7l.8%--e'ster a saponification number of 175",1a--Hellige-color 015 18 and wGardne-rviscosity-of 8'5 centipoises:

Example 9 In an apparatus similar to that described in Example 1;

Xylenewas added to remove-the water'of" After removing 'the carbon byfiltrationand strip Following. removal 7 6-19 grams (equivalent to0.'2745 mol) of linseed oil fatty acids (Acid No. 200.5), 15 grams (equivalent to 0.915

mol) of methyl beta-D-arabinoside (2.8% reducing sugar, M. P. 158-163 C.) and 0.08 gram of calcium oxide was heated rapidly to 156 C. while stirring in a carbon dioxide atmophere. Xylene was added at this point to azeotropically remove the water of reaction. The temperature was maintained between 160 C. and 190 C. for 6 hours; then the xylene was jetted OE With carbon dioxide. After cooling to room temperature, the yield was 89.9 grams of a dark red oil with an acid number of 90.2 (55% ester), a saponification number of 179, a Hellige color of 18+ and a Gardner viscosity at 25 C. of centipoises.

Example 10 was heated rapidly. withhagitationwand. carbon. dioxide.

The. effectofia catalyst on. the. reduction of acidnurnber in theesterification of '1 mol of methyl alpha-D-glucoside with 4 mols of 'linseed.oil fatty acidsat 200" C.

and'23 0' C. in a carbon dioxide, atmosphere, is. illustrated. in, the' following'tablez Ac1dINum-berf.oi Reaction Mixture;

R'eactlorrlimeKhit) .0063molof I .0063m0l of" N 0. Cat. P.b0..per.. No oat. b0 .per.

alyst' mol of alyst' mol "of 3 Fatty I Fatty Acids Acids Example 1 2.

In .anapparatus similar tothat describedin Example 1, 1124' grams (equivalentto. 4' mols). or. linseed. oil fatty acids: (AcidLNoL' 199),. 2037. grams of; methyl alphaD- glucoside- (.1..05-'mol.) and..5..'62 grams .ofllitharge. (.025 2'.

mol). was-..heatedt-rapidly. to-165."? C while stirring .and.

sparging. with.carbon.dioxide Xylene-.wasadded-to en? train thewatenof esterification..: -The reaction was held:

at.;186.1.88. C..for.-1.8. hours; then. :at .2153 .C. for. 1.5

hours. and. finally. at..23.0.-235.. .C... 011 4 hours. .-After.

jetting oh. the. xylenew-ith carbon dioxide and .coolingato.

room'i.temperature,.. 1260. gramsof a: brownishoil was obtained. whichthad an: acid-number. of 4.2, aa saponifica tionnumberrof. 17 6, .a aHelIigecolor of :13 anda viscosity of'165 'centipoises.

I.- claim:

. 1; Atprocesssfon'the.produetion=of -fattyacid-estersof.. "glycosides--mbyg the. direct; esterificatiorr of glyoosides'v with ,1 free :fatty; acids, ,comprising heating a! mixture of; a

glycoside ,from-the=gro.up,\consisting;:0f methyltglycosider and allyl glycoside, and free fatty acid containing about 6 to about 22 carbon atoms in the aliphatic chain in the presence of an alkaline catalyst at a temperature within the range of about C. to about 300 C. until the desired degree of esterification has been attained, said catalyst being from the group consisting of alkali metal hydroxides, alkaline earth oxides, alkali salts of weak acids, and alkaline earth salts of weak acids.

2. Process according to claim 1 wherein said catalyst is present in an amount Within the range of about 0.05 per cent to 0.5 per cent, based on the weight of the fatty acids.

3. Process according to claim 1, wherein said free fatty acid is a mixture of fatty acids obtained by saponification of a vegetable oil.

4. Process according to claim 1, wherein said mixture of free fatty acids is linseed oil fatty acids.

5. Process according to claim 1, wherein said mixture of fatty acids is dehydrated castor oil fatty acid.

The temperature. was. held:

6. Process according to claim 1, wherein said mixture of fatty acids is soy bean oil fatty acids.

7. Process according to claim 1, wherein said fatty acid is stearic acid.

8. Process according to claim 1, wherein said alkaline catalyst is litharge.

9. Process according to claim 1, wherein the water of esterification is removed from the reaction mixture during esterification.

10. Process according to claim 1, wherein the temperature is gradually increased during the esterification.

11. Process according to claim 1, wherein the temperature is increased stepwise during the esterification.

12. Process according to claim 1, wherein the water of esterification is removed by azeotropic distillation.

13. Process for the production of a linseed oil fatty acid tetraester of methyl glucoside, comprising heating a mixture of methyl glucoside, linseed oil fatty acids, xylene, and litharge at a temperature increased stepwise within the range of about 165 C. to 270 C. for 6 hours, under an atmosphere of carbon dioxide; the water of esterification being continuously removed by azeotropic distillation with xylene; the molar ratio of linseed oil fatty acids to methyl glucoside being at least 4:1, said litharge being present in an amount of about 0.05 percent, based on the weight of the linseed oil fatty acids.

14. Process for the production of linseed oil fatty acids tetraester of methyl glucoside, comprising heating a mixture of linseed oil fatty acids, methyl glucoside, xylene, and an alkaline earth acetate, at a temperature within the range of about 225 C. to about 235 C. for 7 hours, under an atmosphere of nitrogen; the water of esterification being continuously removed by azeotropic distillation with xylene; the molar ratio of linseed oil fatty acids to methyl glucoside being at least 4:1, said alkaline earth acetate being present in an amount of about 0.5 percent, based on the weight of the linseed oil fatty acid.

15. Process for the production of the stearic acid tetraester of methyl glucoside, stearic acid, xylene, and calcium oxide at a temperature increased stepwise within the range of about 180 C. to about 250 C, for about 12 hours, under an atmosphere of carbon dioxide; the molar ratio of stearic acid to methyl glucoside being at least 4:1, the water of esterification being continuously removed by azeotropic distillation with the xylene, said calcium oxide being present in an amount of about 0.3 percent, based on the weight of the stearic acid.

16. Process for the production of the stearic acid triester of methyl glucoside, comprising heating a mixture of stearic acid, methyl glucoside, xylene, and calcium oxide at a temperature within the range of about 185 C. to about 205 C. for about 6 hours, under an atmosphere of carbon dioxide; the water of esterification being continuously removed by azeotropic distillation with the xylene; the molar ratio of stearic acid to methyl glucoside beingat least 3:1, said calcium oxide being present in an amount of about 0.3 percent, based on the weight of the stearic acid.

17. Process for the production of the linseed oil fatty acids triester of allyl glucoside comprising heating a mixture of linseed oil fatty acids, allyl glucoside, xylene and of calcium oxide, at a temperature within the range of about 194 C. to about 204 C. for about 7 hours; the water of esterification being continuously removed by azeotropic distillation with the xylene; the molar ratio of linseed oil fatty acids to allyl glucoside being about 4:1, said calcium oxide being present in an amount of about 0.1 percent, based on the weight of the linseed oil fatty acids.

18. Process for the production of linseed oil fatty acids diester of methyl arabinoside comprising heating a mixture of linseed oil fatty acids, methyl arabinoside, xylene, and of calcium oxide, at a temperature within the range of about 156 C. to about 190 C. for about 6 hours, under an atmosphere of carbon dioxide; the water of esterification being continuously removed by azeotropic distillation with the xylene; the molar ratio of linseed oil fatty acids to methyl arabinoside being about 3:1, said calcium oxide being present in an amount of about 0.1 percent, based on the weight of the linseed oil fatty acids.

19. Process for the production of linseed oil fatty acids, triester of methyl galactoside, comprising heating a mixture of linseed oil fatty acids, methyl galactoside, xylene and calcium oxide at a temperature within the range of about C. to about 193 C. for about 6 hours, under an atmosphere of carbon dioxide; the water of esterification being continuously removed by azeotropic distillation with the xylene; the molar ratio of linseed oil fatty acids to methyl galactoside being about 4:1, said calcium oxide being present in an amount of about 0.1 percent, based on the weight of the linseed oil fatty acids.

References Cited in the file of this patent UNITED STATES PATENTS 1,668,945 Clarke et a1. May 8, 1928 2,013,034 Cox et al Sept. 3, 1935 2,450,079 Brown Sept. 28, 1948 FOREIGN PATENTS 487,020 Great Britain June 14, 1928 OTHER REFERENCES Wolff et al.: J. Am. Oil. Chem. Soc., 25 (1948), pp. 258-260.

Stacey et al.: Nature, p. 705 (1949).

Gibbons and Jank, J. Am. Oil. Chem. Soc., 29 (1952), pp. 467-469.

Whistler et al.: Polysaccharide Chemistry, page 76, 1953.

Ser. No. 283,323, Chwala (A. P. C.), published Apr. 20, 1943. 

1. A PROCESS FOR THE PRODUCTION OF FATTY ACID ESTERS OF GLYCOSIDES BY THE DIRECT ESTERIFICATION OF GLYCOSIDES WITH FREE FATTY ACIDS, COMPRISING HEATING A MIXTURE OF A GLYCOSIDE, FROM THE GROUP CONSISTING OF METHYL GLYCOSIDE AND ALLYL GLYCOSIDE, AND FREE FATTY ACID CONTAINING ABOUT 6 TO ABOUT 22 CARBON ATOMS IN THE ALIPHATIC CHAIN IN THE PRESENCE OF AN ALKALINE CATALYST AT A TEMPERATURE WITHIN THE RANGE OF ABOUT 160*C. TO ABOUT 300*C. UNTIL THE DESIRED DEGREE OF ESTERIFICATION HAS BEEN ATTAINED, SAID CATALYST BEING FROM THE GROUP CONSISTING OF ALKALI METAL HYDROXIDES, ALKALINE EARTH OXIDES, ALKALI SALTS OF WEAK ACIDS, AND ALKALINE EARTH SALTS OF WEAK ACIDS. 